Inflatable supports

ABSTRACT

An inflatable support is made of a vapour permeable material capable of sustaining an inflated state for significant periods without replenishment so as to provide good pressure distribution whilst allowing breathing to prevent sweating.

This invention relates to an inflatable support means and, in particularbut not exclusively, to an inflatable tissue support for preventionand/or repair of tissue pressure damage.

It is generally known that people who remain in static positions forlong periods (e.g. the seriously injured, the brittle boned, unconsciouspatients, the elderly and those with certain disabilities) areparticularly susceptible to pressure injuries such as decubitus ulcersor bed sores. These factors are exacerbated by the need to lie on hardsurfaces such as theatre tables or firm plastic-covered mattresses.

Considerable resources in terms of nursing and extended hospitalisationare spent on the treatment of patients of all ages and conditions whodevelop pressure sores. According to one estimate over .English Pound.2billion is spent annually on the prevention and treatment of pressuresores. To date, most preventive measures have been expensive either interms of increased nursing care, e.g. regular repositioning or in termsof equipment. Such equipment includes specialist units such as a netsuspension bed or hammock, water beds or mattresses, air beds orcushions (both conventional and ripple-type). All this equipment iscomplex and expensive and the expense is difficult to justify except forthose patients who have developed acute conditions. Additionally, thisequipment is only partially effective.

There are many types of airbeds or cushions, and these typically areporous adjacent the patient so that air escapes from the air bed orcushion to ventilate the patient and prevent sweating. This howevermeans that the airbed or cushion must be continually supplied with airfrom a blower to prevent it deflating. This is extravagant in terms ofstorage space, equipment cost and running costs. Another form of supportconsists of an array of interconnected egg-shaped inflatable cellsdesigned to keep the patient's body immersed in the cushion. The designis costly to implement, does not allow the patient's skin to breath andis believed still to generate local pressure points.

In attempting to provide a simple and effective support for preventing atreating pressure sores which may be implemented at relatively low cost,we have unexpectedly found that it is possible to provide an inflatablesupport made of a material which transmits water vapour in sufficientamounts to allow a patient's skin to breathe whilst being substantiallyimpermeable to air so that the support can stay inflated for longperiods without requiring replenishment. The reason for this remarkableeffect are not yet fully understood, but it is believed that it mayarise because when the material is inflated and thus subjected tostress, the normal vapour permeability is inhibited thus preventingescape of the inflation medium. But the continual voluntary andinvoluntary movement of the user stresses and relaxes the material andthus momentarily causes local areas of the material to allow vapour topermeate.

Accordingly in one aspect this invention provides an inflatable supportmeans formed of a breathable or vapour permeable material capable ofsustaining an inflated state.

Thus, in use, the support provides the benefits of pressure distributionwhilst allowing breathing of water vapour. The support may stay inflatedfor long periods so that it is not necessary to provide a continualsource of inflation medium under pressure.

Advantageously, said material has a water vapour transmission rate inthe range of from 50 to 400 g/m².d, preferably in the range of from100-300 and ideally about 200 g/m².d.

The material is preferably a polyurethane film such as, e.g. athermoplastic polyester urethane elastomer film.

The thickness of the material preferably lies in the range of from 25 μmto 100 μm and ideally in the range of from 50 μm to 80 μm. This providessufficient strength whilst preserving vapour permeability.

The material is preferably made by coextrusion with a suitable carrierfilm. The material is preferably bonded together e.g. by heat sealing orwelding to form a plurality of inflatable cells, which areadvantageously interconnected to allow the inflation medium to passtherebetween.

In some applications, there may be a valve means for controlling theflow between said cells whereby the volume or pressure within a cell maybe adjusted to a required level and the support means may include aninlet means for an inflation medium and means for sealing said inletmeans.

The support means has many different uses, for example it may beconfigured for use as an interface between at least part of the body ofa user and a support, or as an interface between an external supportshape splint and a part of the body of a user. Furthermore theinflatable support may be used inside the body to provide support forthe internal organs of a patient.

The support means may include attachment means such as adhesive tabs forallowing the support means to be secured around at least part of thebody of a user.

In another aspect the invention provides a protective article for beingsecured around a part of a body of a user, the protective article beingformed of a breathable or vapour permeable material and being configuredto be spaced from a wound site or similar on the user's body and,optionally, including means for sealing or securing the article to thebody.

In yet another aspect of this invention there is provided a protectivearticle for being fitted around a part of a body of a user to preventwater reaching said body part, said protective article being formed of abreathable or vapour permeable material and, optionally, including meansfor sealing or securing the article to the body.

Whilst the invention has been defined above it extends to any inventivecombination of the features set out above or in the followingdescription.

The invention may be performed in various ways and certain embodimentsthereof will now be described in detail, reference being made to theaccompanying drawings, in which:

FIG. 1 is a plan view of an inflatable support interface beforeinflation and sealing;

FIG. 2 is a perspective view of an inflated contoured supportmattresses;

FIG. 3 shows an arrangement consisting of an outer structural splint andan inner inflated support interface;

FIG. 4 shows a protective mitten, and

FIG. 5 shows a protective sock.

Referring initially to FIG. 1, there is shown a plain inflatableinterface 10 which could be located, for example beneath the buttocks ofa bedbound or chairfast person. The interface comprises a sheet ofextruded thermoplastic polyester urethane film folded and then heatwelded along lines 12 to form a series of parallel interconnected cells14 which inflate into a generally cylindrical shape. Instead of or inaddition to heat welding, other bonding techniques may be used, forexample adhesives, r.f. welding etc. The interface is inflated throughan inlet 16 which is shown here as an inlet tube with a sealing stopper,but other inlet/seal arrangements may be used. For example, a "break"may be left in one of the weld lines 12 to allow inflation whereafterthe break is sealed by heat welding. In the illustrated example, asingle sheet of film is used to form the interface support, but ifrequired the support may be formed from double sheets.

This type of support will normally stay sufficiently inflated for aperiod of months. If, however, in extreme conditions the support doesdeflate significantly it can be reinflated from time to time, e.g. onceper nursing shift. Thus no inflation equipment is required to bepermanently attached.

The inflatable interfaces may come in many different configurationsdepending on the particular application. For example, if an ankle cuffsupport is required a generally rectangular multi-celled interface ofthe type shown in FIG. 1 may be provided with adhesive tags so that theinterface may be wrapped around the ankle and then secured in place.

Referring to FIG. 2, the support mattress 20 formed of thermoplasticpolyester urethane film to provide cells 21 in a similar manner asbefore. In this case however, complex geometric patterns are producedand skin contact is eliminated from specific areas e.g. at the back ofthe head (region 22), the buttocks (region 24) and the right calf(region 26). With this system the cells 21 may be interlinked to provideuniform hydrostatic pressure to the skin but, if required, certain cellscan be isolated and include valves (not shown) to create a higher orlower pressure. The mattress of FIG. 2 also includes an elevator 28 forthe left leg, and the elevator includes an inlet 30 for inflating themattress.

Referring to FIG. 3 this illustrates a specialised splint 40 (e.g. toaid repair of tissue damage with an established haemophiliac) for theleft ankle and foot. Firstly an outer splint 42 is constructed in anormal way using conventional materials (e.g. Plasterzote [TM]) withstrapping 44 (e.g. Velcro [TM]). The outer splint 42 is made larger thannormal so that a "sock" shaped cushion support 46 of thermoplasticpolyester urethane film can be inserted into the splint support.

When fitted to the patient, the sock can be inflated through an inletvalve 48 to provide adequate support. The pressure in the sock 46 can beeasily adjusted to provide patient comfort at all times.

In the embodiment of FIG. 4, a protective shield 50 for a burns patientis provided by securing a sheet of breathable thermoplastic polyesterurethane film around the affected area, preferably inflating the film orotherwise minimising the possibility of the film contacting the affectedarea. Thus, for example, as shown an oversize mitten 50 may be providedfor a patient with burns on a hand, the mitten having a cuff 52 whichcan be secured around an unaffected part of the wrist and preferablyprovided with a seal. The cuff may carry a suitable adhesive for thispurpose.

In a further embodiment shown in FIG. 5, a protective shield 60 for theleg of a patient suffering from oedema and requiring water bathtreatment is shown. The shield 60 consists of a breathable thermoplasticpolyester urethane film in the form of a long sock having a garter strip62 carrying suitable adhesive for bonding it around the leg of a user.If required, the garter strip 62 may also effect sealing against theingress of water. In use, the shield is fitted over the leg of thepatient, evacuated and then bonded and sealed to the leg of the user.

In a yet further embodiment, a support may be made by filling a pouch ofbreathable thermoplastic polyester urethane film with polystyrene beadsor other free-flowing particles, fitting the pouch around or beneath thepart to be supported and then evacuating and sealing the pouch. Aspreviously the film breathes yet is impermeable to air and so is capableof preserving the vacuum necessary to maintain its contour.

In each of the above embodiments, the breathable thermoplastic film hasbeen a blown film extruded from thermoplastic polyester urethaneelastomer which has been produced by coextrusion with a polyethylenecarrier film. The elastomer film, when removed from the carrier,provides a film which we have found allows transmission of water vapourat a rate sufficient to prevent sweating, but which is substantiallyimpermeable to air. Thus the inflated articles can sustain theirinflated state for long periods which means that it is not normallynecessary to re-inflate or top up the supports in use. Supports of thetype shown in FIG. 1 have been used for several months withoutsignificantly deflating.

One example of a suitable material is a thermoplastic polyurethaneelastomer film known as Platilon (Registered Trade Mark) UO1,manufactured and marketed by Deutsche Atochem Werke in Germany, althoughother materials having similar properties may be used. Two differentnominal thickness have been used, 50 μm and 80 μm. The material has asegmented (i.e. alternating rigid and soft segments) and generallylinear structure, and has what is termed a "slightly blocking" surfacewhich gives it an anti-slip property. The material has a rubber-likeelasticity with a low Young modulus and is capable of extreme elongationwhilst having good abrasion resistance.

The water vapour transmission rate for a typical sample of material 50μm thick is about 200 g/m².d but suitable performance can be achievedwith materials having a value in the range of from 50 to 400 andpreferably from 100 to 300 g/m².d. Likewise, a typical sample of thematerial has a tensile strength of 55 N/mm² with an elongation of 700%at failure, and the Young modulus is below 100 MPa, preferably below 50MPa and ideally between 2 and 10 MPa.

In addition to the breathing properties of these types of material,their elasticity qualities provide excellent pressure reliefcharacteristics, because the material yields elastically to spread theload over a wider area when a load is applied to the inflated cell. Intests we have found that, with a typical loading, the sensed pressureapplied to the patient's skin approached the theoretical minimum.

Furthermore, the anti-slip properties in combination with the elasticitymean that the surface of the interface tends to move with the skin ofthe user without applying a high shear to the adjacent tissue of thepatient and this is believed to alleviate some of the contributoryfactors of pressure sores.

Moreover, the thermal conductivity of the film is sufficient to reducethe local heating that often occurs around the site of a potentialpressure sore thus exacerbating the condition.

Although we mention a specific group of films other materials may beused provided they are capable of sustaining a sufficiently inflatedstate for, say, several hours, whilst still allowing water vapour topermeate. Other suitable materials may be selected by one skilled in theart.

I claim:
 1. An inflatable support means for being inflated and sealed inuse to support at least part of the body of a user, said support meansincluding envelope means comprising a sheet of material that ispermeable to water vapor but substantially impermeable to air to theextent of sustaining an inflated state by virtue of air pressure alone,said sheet having a water vapor transmission rate from 50 to 400 g/m² d,an inlet for inflation medium and means for sealing said inlet.
 2. Aninflatable support means according to claim 1, wherein said material hasa water vapour transmission rate in the range of from 100-300 andideally about 200 g/m².d.
 3. An inflatable support means according toclaim 1, wherein said material is a polyurethane film.
 4. An inflatablesupport means according to claim 3, wherein said polyurethane film is athermoplastic polyester urethane elastomer film.
 5. An inflatablesupport means according to claim 1, wherein the thickness of saidmaterial lies in the range of from 25 μm to 100 μm.
 6. An inflatablesupport means according to claim 5, wherein said thickness lies in therange of from 50 μm to 80 μm.